PROJECT SUMMARY: This R01 renewal proposal aims to advance the next generation of optical nanomaterial probes for ultrasensitive detection of diseased lesions in vivo, with applications to fluorescence- guided surgery (FGS). The emerging field of FGS currently lacks the pipeline of optical contrast agents that can illuminate such deep-seated lesions to permit real-time detection and precise excision by oncosurgeons. Our previous R01 project developed the first generation of lesion-targeted optical probes based on rare-earth (RE)-doped nanocomposites that can delineate cancer lesions in vivo but are not optimal for FGS applications. They have relatively high signal attenuation and require near-infrared (NIR) light for excitation, whose shorter penetration depth limits the ability to reach and detect deeper-seated lesions. Therefore, this R01 renewal application will focus on continuing our advance by designing significantly brighter SWIR-emitting nanoprobes, while broadening the context for SWIR imaging along two important pathways: First, we aspire to develop a class of an order-of-magnitude brighter SWIR emitting nanocomposites that can be excited using SWIR light, with the hypothesis that they can be excited using deeper-penetrating IR light, which will open up applications in illuminating cancers around deeper-seated retroperitoneal nodes (Aim 1A) and precisely target these to cancer-lesions in the surgical bed (Aim 1B). Secondly, we aim to develop a live-subject SWIR imaging platform that can guide precision detection of small cancer clusters in vivo (Aim 2A) and molecularly map the surgical bed to demarcate anatomical landmarks of tumor lesions, lymph nodes and para-aortic vessel endothelium (Aim 2A). We will extend this live-subject imaging platform to guide complete excision and demonstrate superior excision outcomes relative to those guided by existing fluorophores and our first generation NIR excitable RE nanoprobes (Aim 2B). The outcomes of Aim 2 will be demonstrated using an ovarian cancer peritoneal metastasis and debulking model. The overall impact of this project will be on the design of a surveillance nanotechnology based on a new class of contrast agents that can be integrated within a short wave infrared-light imaging platform technology for fluorescence-surgery guidance.